brainwashed ?

So I have been dating my boyfriend for 3 years and we are both virgins. I am 18 and I'm on birth control. I have decided I want to have to have sex with my boyfriend that I love with all my heart. We have already made it clear we are going to use a condom also. However , why am I still terrified im going to get pregnant ? Am I brainwashed into thinking no matter how safe I am it's still going to happen... my grandmother got pregnant at 19 but she didn't even use a condom. I just feel like now all my doctors are like you can still get pregnant using a condom and birth control... so that coming from a doctor is scary. Idk if they are just trying to scare me so I wait or what. I am completely comfortable with my boyfriend but I don't wanna be having sex and be like omg. Because I'm already a super paroniod person. How serious am I suppose to make this event ?! Like is it just suppose to be calm and chill or is this a big freaking deal.